File : s-taprob.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
4 -- --
5 -- S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
10 -- --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 -- This package provides necessary definitions to handle simple (i.e without
33 -- entries) protected objects.
34
35 -- All the routines that handle protected objects with entries have been moved
36 -- to two children: Entries and Operations. Note that Entries only contains
37 -- the type declaration and the OO primitives. This is needed to avoid
38 -- circular dependency.
39
40 -- This package is part of the high level tasking interface used by the
41 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
42 -- (aka GNARLI, GNU Ada Run-time Library Interface)
43
44 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
45 -- Any changes to this interface may require corresponding compiler changes
46 -- in exp_ch9.adb and possibly exp_ch7.adb and exp_attr.adb
47
48 package System.Tasking.Protected_Objects is
49 pragma Elaborate_Body;
50
51 ---------------------------------
52 -- Compiler Interface (GNARLI) --
53 ---------------------------------
54
55 -- The compiler will expand in the GNAT tree the following construct:
56
57 -- protected PO is
58 -- procedure P;
59 -- private
60 -- open : boolean := false;
61 -- end PO;
62
63 -- protected body PO is
64 -- procedure P is
65 -- ...variable declarations...
66 -- begin
67 -- ...B...
68 -- end P;
69 -- end PO;
70
71 -- as follows:
72
73 -- protected type poT is
74 -- procedure p;
75 -- private
76 -- open : boolean := false;
77 -- end poT;
78 -- type poTV is limited record
79 -- open : boolean := false;
80 -- _object : aliased protection;
81 -- end record;
82 -- procedure poPT__pN (_object : in out poTV);
83 -- procedure poPT__pP (_object : in out poTV);
84 -- freeze poTV [
85 -- procedure poTVI (_init : in out poTV) is
86 -- begin
87 -- _init.open := false;
88 -- object-init-proc (_init._object);
89 -- initialize_protection (_init._object'unchecked_access,
90 -- unspecified_priority);
91 -- return;
92 -- end _init_proc;
93 -- ]
94 -- po : poT;
95 -- poTVI (poTV!(po));
96
97 -- procedure poPT__pN (_object : in out poTV) is
98 -- poR : protection renames _object._object;
99 -- openP : boolean renames _object.open;
100 -- ...variable declarations...
101 -- begin
102 -- ...B...
103 -- return;
104 -- end poPT__pN;
105
106 -- procedure poPT__pP (_object : in out poTV) is
107 -- procedure _clean is
108 -- begin
109 -- unlock (_object._object'unchecked_access);
110 -- return;
111 -- end _clean;
112 -- begin
113 -- lock (_object._object'unchecked_access);
114 -- B2b : begin
115 -- poPT__pN (_object);
116 -- at end
117 -- _clean;
118 -- end B2b;
119 -- return;
120 -- end poPT__pP;
121
122 Null_Protected_Entry : constant := Null_Entry;
123
124 Max_Protected_Entry : constant := Max_Entry;
125
126 type Protected_Entry_Index is new Entry_Index
127 range Null_Protected_Entry .. Max_Protected_Entry;
128
129 type Barrier_Function_Pointer is access
130 function
131 (O : System.Address;
132 E : Protected_Entry_Index)
133 return Boolean;
134 -- Pointer to a function which evaluates the barrier of a protected
135 -- entry body. O is a pointer to the compiler-generated record
136 -- representing the protected object, and E is the index of the
137 -- entry serviced by the body.
138
139 type Entry_Action_Pointer is access
140 procedure
141 (O : System.Address;
142 P : System.Address;
143 E : Protected_Entry_Index);
144 -- Pointer to a procedure which executes the sequence of statements
145 -- of a protected entry body. O is a pointer to the compiler-generated
146 -- record representing the protected object, P is a pointer to the
147 -- record of entry parameters, and E is the index of the
148 -- entry serviced by the body.
149
150 type Entry_Body is record
151 Barrier : Barrier_Function_Pointer;
152 Action : Entry_Action_Pointer;
153 end record;
154 -- The compiler-generated code passes objects of this type to the GNARL
155 -- to allow it to access the executable code of an entry body.
156
157 type Entry_Body_Access is access all Entry_Body;
158
159 type Protection is limited private;
160 -- This type contains the GNARL state of a protected object. The
161 -- application-defined portion of the state (i.e. private objects)
162 -- is maintained by the compiler-generated code.
163 -- Note that there are now 2 Protection types. One for the simple
164 -- case (no entries) and one for the general case that needs the whole
165 -- Finalization mechanism.
166 -- This split helps in the case of restricted run time where we want to
167 -- minimize the size of the code.
168
169 type Protection_Access is access all Protection;
170
171 Null_PO : constant Protection_Access := null;
172
173 function Get_Ceiling
174 (Object : Protection_Access) return System.Any_Priority;
175 -- Returns the new ceiling priority of the protected object
176
177 procedure Initialize_Protection
178 (Object : Protection_Access;
179 Ceiling_Priority : Integer);
180 -- Initialize the Object parameter so that it can be used by the runtime
181 -- to keep track of the runtime state of a protected object.
182
183 procedure Lock (Object : Protection_Access);
184 -- Lock a protected object for write access. Upon return, the caller
185 -- owns the lock to this object, and no other call to Lock or
186 -- Lock_Read_Only with the same argument will return until the
187 -- corresponding call to Unlock has been made by the caller.
188
189 procedure Lock_Read_Only (Object : Protection_Access);
190 -- Lock a protected object for read access. Upon return, the caller
191 -- owns the lock for read access, and no other calls to Lock with the
192 -- same argument will return until the corresponding call to Unlock
193 -- has been made by the caller. Other calls to Lock_Read_Only may (but
194 -- need not) return before the call to Unlock, and the corresponding
195 -- callers will also own the lock for read access.
196
197 procedure Set_Ceiling
198 (Object : Protection_Access;
199 Prio : System.Any_Priority);
200 -- Sets the new ceiling priority of the protected object
201
202 procedure Unlock (Object : Protection_Access);
203 -- Relinquish ownership of the lock for the object represented by
204 -- the Object parameter. If this ownership was for write access, or
205 -- if it was for read access where there are no other read access
206 -- locks outstanding, one (or more, in the case of Lock_Read_Only)
207 -- of the tasks waiting on this lock (if any) will be given the
208 -- lock and allowed to return from the Lock or Lock_Read_Only call.
209
210 private
211 type Protection is record
212 L : aliased Task_Primitives.Lock;
213 -- Lock used to ensure mutual exclusive access to the protected object
214
215 Ceiling : System.Any_Priority;
216 -- Ceiling priority associated to the protected object
217
218 New_Ceiling : System.Any_Priority;
219 -- New ceiling priority associated to the protected object. In case
220 -- of assignment of a new ceiling priority to the protected object the
221 -- frontend generates a call to set_ceiling to save the new value in
222 -- this field. After such assignment this value can be read by means
223 -- of the 'Priority attribute, which generates a call to get_ceiling.
224 -- However, the ceiling of the protected object will not be changed
225 -- until completion of the protected action in which the assignment
226 -- has been executed (AARM D.5.2 (10/2)).
227
228 Owner : Task_Id;
229 -- This field contains the protected object's owner. Null_Task
230 -- indicates that the protected object is not currently being used.
231 -- This information is used for detecting the type of potentially
232 -- blocking operations described in the ARM 9.5.1, par. 15 (external
233 -- calls on a protected subprogram with the same target object as that
234 -- of the protected action).
235 end record;
236
237 procedure Finalize_Protection (Object : in out Protection);
238 -- Clean up a Protection object (in particular, finalize the associated
239 -- Lock object). The compiler generates calls automatically to this
240 -- procedure
241
242 end System.Tasking.Protected_Objects;